Method of constructing a transformer winding assembly

ABSTRACT

Winding sections are assembled coaxially with one of the winding sections being of the encapsulated type. The encapsulated winding section is cast in a mold having depressions thereon which form projections on the surfaces of the encapsulated winding section. The projections separate adjacent winding sections from the encapsulated winding section and form spaces therebetween which permit the flow of cooling dielectric.

United States Patent [1 1 j 2/ 1970 l-lofrnann et al. 264/272 Eley Nov. 27, 1973 [54] METHOD OF CONSTRUCTING A 3,201,728 8/1965 Mcwhirter 336/60 TRANSFORMER WINDING ASSEMBLY 3,071,845 1/1963 Leonard et al. 29/605 3,611,226 10/1971 Cotton et al. 336/60 Inventor: Edgar Eley, Athens, 2,856,639 10/1958 Forrest 61 a1. 264/272 x [73] Assignee: Westinghouse Electric Corporation,

Pittsburgh Przmary Exammer-Charles W. Lanham Assistant ExaminerCarl E. Hall [22] Flled: June 29, 1972 AttorneyA. T. Stratton et a1.

[21] Appl. No.: 267,290

. [57] ABSTRACT 52 US. Cl 29/605, 29/602, 264/272, Winding Sections are assembled eeexially with one of v 336/60, 336/96, 33 the winding sections being of the encapsulated type. 51 1m. Cl. H01: 7/06 The encapsulated Winding Section is east in a mold [58] Field 6: Search 29/602, 605; 336/60, having depressions thereon which form projections en 3 205 58, 9 0; 2 272 the surfaces of the encapsulated winding section. The projections separate adjacent winding sections from 5 References Cied the encapsulated winding section and form spaces UNITEDSTATES PATENTS therebetween which permit the flow of cooling dielectric. 3,559,134 1/1971 Daley 336/96 1 4 Claims, 5 Drawing Figures Patented Nov.

tion operations. I

. 1 METHOD or CONSTRUCTING A TRANSFORMER WINDING ASSEMBLY BACKGROUND OFTHE INVENTION the heat generated by losses'in the winding structure.

An effective arrangement for distribution-type power transformers uses an encapsulated high-voltage winding section disposed between inner and outer nonencapsulated low-voltage winding sections. With this arrangement, the inner low-voltage winding section is positioned inside an opening inthe encapsulated winding section and the outer low-voltage winding section is wound over the outside of the encapsulated winding section. The heat generated within the encapsulated winding section is transferred to the cooling media which normally consists of mineral oil. Generally, the greater thesur'facearea of the encapsulated winding section which is exposed to the oil, the better the heat transfer. Thus, it is desirable to expose as much of the encapsulated winding section to the oil as possible.

Therefore, it is desirable, and it is an object of this invention, to provide a method of constructing a transformer winding assembly wherein the encapsulated winding section is exposed, as much as practicable, to the coolant of the transformer. It is also desirable, and it is another object of this invention, to provide the cooling areas by convenient and inexpensive, construc- SUMMARY OF THE INVENTION 7 7 There is disclosed herein anew" and useful method of constructing a transformer winding assembly which provides excellent heat transfer from an encapsulated winding section to the cooling dielectric. A plurality of winding sections are wound and one winding section is encapsulated. The winding sections are assembled coaxially with each other. Parallel projections are formed on the surface of the encapsulated winding section by the encapsulating material due to the construction of the mold used for encapsulation. These projections form spaces between adjacent winding sections and the encapsulated winding section through which the cooling dielectric of the transformer flows.

BRIEF DESCRIPTION OF THE DRAWINGS Further advantages and uses of this invention will become more apparent when considered in view of the FIG. 4 is a view of another mold assembly which may DESCRIPTION OF THE PREFERRED EMBODIMENT Throughout the following description, similar reference characters refer to similar members in all the figures of the drawings.

Referring now to the drawings and FIG. 1 in particular, there is shown a transformer constructed according to the teachings of this invention. The transformer includes the magnetic cores l0 and 12 and the winding assembly 14. The transformer illustrated in FIG. I is constructed of components suitable for power distribution transformers, and primarily for distribution transformers of the pole-mounted type; The transformer shown may be placed in a tank enclosure containing a suitable coolant, such as mineral oil. J In the view shown in FIG. 1, the magneticcoresl0 and 12 are wound types, although other types maybe used within. the contemplation of this invention..The winding assembly 14 includes an inner low-voltage winding section 16, an encapsulated high-voltage winding section 18, and anouterlow-voltage winding section 20. The winding assembly 14 contains an opening 22 throughv which the magnetic cores wand 12 extend. Although not shown, the winding sections 16, 18 and 20 have leads extending therefrom to permit electrical connection to each other and/or to other electrical apparatus.

The inner low-voltage winding section 16 comprises a plurality of layers of conductors and insulation 'positioned around the magnetic cores l0 and 12. The conductors may be in the form of wire stands, foilsheets, or in any other form suitable for the type of the trans former. Strips of insulation may be placed between insulation layers to enhance the thermal characteristics of the winding section 16 by allowing fluid coolant to, flow between the insulation layers.

The encapsulated winding section 18 is disposed around the inner low-voltage winding section-l6. The

encapsulated winding section .18 comprises a plurality of layers of conductors with a suitable encapsulating material, such as an epoxy resin, cast over the conductors. The conductors of the encapsulated winding section 18 are normally formed by layers of foil sheet with a suitable insulation therebetween; however, other forms of conductors may-be used.

The outer-low voltage winding section 20 comprises a plurality of layers of conductors and insulation positioned concentrically with the encapsulated winding section 18. Construction and materials for the outer low-voltage winding section 20 are similar to the inner low-voltage winding section 16. The outer low-voltage winding section 20 is separated from the encapsulated winding section 18 by a suitable means, such as by the spacing members 24. The spacing members 24 permit the flow of cooling dielectric adjacent to the encapsulated winding section 18. Consequently heat from the encapsulated winding section 18 is transferred to the cooling dielectric of the transformer.

FIG. 2 illustrates the encapsulated winding section 18 and the spacing members 24 in more detail; The encapsulated winding section 18 has a substantially rectangular shape with a substantially rectangular opening 26 14. The projections 36.form spaces between the outer low-voltage winding section and the encapsulated winding-section 18 through which cooling dielectric Projections 36'are conveniently formed from the'encapsulating material during the encapsulating process. Depressions in the'casting mold corresponding to the size and positions of the projections 36 allow the encapsulating material to project from the surface of the outer sides 32 and 34. Thus, without any extra work being required, the projections 36 may beplaced into the winding assembly 14 to improve the thermalcharacteristics of the winding assembly 14.

FIG. 3 illustrates a mold assembly which may be used to encapsulate the winding section 18 shown in FIG. 2. The mold assembly includes the complementary mold portions 54 and 56 and the center mold portion 58. The winding section being encapsulated is placed into the space around the center mold portion 58 and encapsulating material is injected into the mold assembly. The depressions 60 in the complementary mold portions 54 and 56 allow the encapsulating material to form the projections 36 on the encapsulated winding section 18. Each depression hasa longitudinal dimension which is parallel to the axis of the winding section being encapsulated. Although illustrated with a rectangular crosssectional shape, the depressions may have other crosssectional shapes, such as triangular and semicircular.

Construction of the mold assembly may be similar to the mold disclosed in US. Pat. No. 3,537,677 which is assigned to the same assignee as this invention. It is within the contemplation of this invention that the depressions 60 may be provided by inserting a mold liner into a mold having substantially smooth surfaces. The mold liners would have depressions formed therein corresponding to the desired projections on the encapsulated winding section. With this arrangement, th size and number of the depressions could easily be changed by inserting different mold liners into the mold assembly.

If additional projections on the encapsulated winding section 18 are desired, the mold assembly shown in FIG. 4 may be used. The outer mold portions 62, 64, 66, and 68 each have depressions 60 on their inner surfaces. The center mold portion 70 contains depressions 60 around its entire outer surface. The mold assembly shown in FIG. 4 would provide an encapsulated winding section with projections located around all of the inner and outer sides of the encapsulated winding section.

Additional cooling spaces may be proivded for the encapsulated winding section 18 shown in FIG. 2 by the spacing members 24. The spacing members 24 are secured in the winding assembly 14 by the insulating material 44 and by an adhesive placed therebetween. The spacing members 24 may be constructed of any suitable material, such as pressboard strips, and the insulating material 44 may comprise kraft paper. The spacing members 24 have an outer surface 46 defined by parallel edges 48 and 50. Although illustrated in an exploded view, the spacing members 24 are positioned adjacent to the side 28 of the encapsulated windingsection 18 in the complete winding assembly 14. Although not illustrated, similar spacing members may be positioned adjacent to the end 30 of the encapsulated winding section 18. I

FIG. 5 is a top plan view of a winding assembly having an encapsulated winding section 18 with projections 36 on its inner and outer sides. The projections 36 separate the encapsulated winding section 18 from the inner low-voltage winding section 16 and from the outer low-voltage winding section 20. The projections 36 are an integral part of the encapsulating material and form openings 35 between the winding sections through which cooling dielectric may flow. The encapsulated winding section 18 shown in FIG. 5 may be constructed using the mold shown in FIG. 4.

With the novel construction method taught by this invention, substantial improvements in the thermal characteristics of the winding assembly may be realized without significantly affecting the manufacturing cost of the winding assembly. Since numerous changes may be made in the above described method and different embodiments of the invention may be made, without departing from the spirit thereof, it is intended that all of the matter contained in the foregoing description or shown in the accompanying drawings shall be interpreted as illustrative rather than limiting.

I claim as my invention:

1. A method of, constructing a transformer winding assembly comprising the steps of:

winding first, second and third windingsections, providing mold means having surfaces with depressions thereon, each of said depressions having a longitudinal dimension, placing said second winding section into said mold means with the axis of said second winding section parallel to the longitudinal dimensions of said depressions, encapsulating said second winding section while positioned in said mold means to provide an encapsu lated winding section having integral projections on at least one side thereof, and j assembling said winding sections coaxially, with said encapsulated winding section positioned around said first winding section and said third winding section positioned around said encapsulated winding section. 2. The method of constructing a transformer winding assembly of claim 1 wherein the mold means includes an outer mold portion and an inner mold portion, the depressions existing only on the outer mold portion to provide an encapsulated winding section having integral projections on only the outside thereof.

3. The method of constructing a'transformer winding assembly as claim 1 wherein the mold means includes an outer mold portion and an inner mold portion, the depressions existing only on the inner mold portion to provide an encapsulated winding section having integral projections on only the inside thereof.

4. The method of constructing a transformer winding assembly of claim 1 wherein the mold means includes an outer mold portion and an inner mold portion, the depressions existing on both said inner and outer mold portions to provide an encapsulated winding section having integral projections on both sides thereof. 

1. A method of constructing a transformer winding assembly comprising the steps of: winding first, second and third winding sections, providing mold means having surfaces with depressions thereon, each of said depressions having a longitudinal dimension, placing said second winding section into said mold means with the axis of said second winding section parallel to the longitudinal dimensions of said depressions, encapsulating said second winding section while positioned in said mold means to provide an encapsulated winding section having integral projections on at least one side thereof, and assembling said winding sections coaxially, with said encapsulated winding section positioned around said first winding section and said third winding section positioned around said encapsulated winding section.
 2. The method of constructing a transformer winding assembly of claim 1 wherein the mold means includes an outer mold portion and an inner mold portion, the depressions existing only on the outer mold portion to provide an encapsulated winding section having integral projections on only the outside thereof.
 3. The method of constructing a transformer winding assembly as claim 1 wherein the mold means includes an outer mold portion and an inner mold portion, the depressions existing only on the inner mold portion to provide an encapsulated winding section having integral projections on only the inside thereof.
 4. The method of constructing a transformer winding assembly of claim 1 wherein the mold means includes an outer mold portion and an inner mold portion, the depressions existing on both said inner and outer mold portions to provide an encapsulated winding section having integral projections on both sides thereof. 